"if ($foo == ($bar->{c}{d}{e}//'moo')) { ... }"

You may have typed that in a hurry. While I do follow the gist of what you're saying, I do hope you're aware that '==' is used for numbers (e.g. 300) and 'eq' is used for strings (e.g. "moo"). See "perlop: Equality Operators" for more complete details.